Saw this engine listed for sale (wishing I'd bought it now). GA16 for sale/sold

The comments from the seller are that "A" series gearbox bolts straight up.

GA16s have 76 bore and 88mm stroke (not so keen on the latter aspect). Apparently around 105HP std.

Does anyone know much about these engines? Wonder if the bellhousing pattern for this example had somehow been modified? (this would be an unusual?) Wonder how far off the head gasket pattern is from an A series? (bore is comparable) Are the heads a good design?

Food for thought.